DOMUtils


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57  
58  package org.apache.soap.util.xml;
59  
60  import org.w3c.dom.*;
61  
62  /**
63   * @author Matthew J. Duftler
64   * @author Sanjiva Weerawarana
65   */
66  public class DOMUtils {
67    /**
68     * The namespaceURI represented by the prefix <code>xmlns</code>.
69     */
70    private static String   NS_URI_XMLNS = "http://www.w3.org/2000/xmlns/";
71  
72    /**
73     * Returns the value of an attribute of an element. Returns null
74     * if the attribute is not found (whereas Element.getAttribute
75     * returns "" if an attrib is not found).
76     *
77     * @param el       Element whose attrib is looked for
78     * @param attrName name of attribute to look for 
79     * @return the attribute value
80     */
81    static public String   getAttribute (Element el, String   attrName) {
82      String   sRet = null;
83      Attr   attr = el.getAttributeNode(attrName);
84  
85      if (attr != null) {
86        sRet = attr.getValue();
87      }
88      return sRet;
89    }
90  
91    /**
92     * Returns the value of an attribute of an element. Returns null
93     * if the attribute is not found (whereas Element.getAttributeNS
94     * returns "" if an attrib is not found).
95     *
96     * @param el       Element whose attrib is looked for
97     * @param namespaceURI namespace URI of attribute to look for 
98     * @param localPart local part of attribute to look for 
99     * @return the attribute value
100    */
101   static public String   getAttributeNS (Element el,
102                                        String   namespaceURI,
103                                        String   localPart) {
104     String   sRet = null;
105     Attr   attr = el.getAttributeNodeNS (namespaceURI, localPart);
106 
107     if (attr != null) {
108       sRet = attr.getValue ();
109     }
110 
111     return sRet;
112   }
113 
114   /**
115    * Concat all the text and cdata node children of this elem and return
116    * the resulting text.
117    *
118    * @param parentEl the element whose cdata/text node values are to
119    *                 be combined.
120    * @return the concatanated string.
121    */
122   static public String   getChildCharacterData (Element parentEl) {
123     if (parentEl == null) {
124       return null;
125     } 
126     Node          tempNode = parentEl.getFirstChild();
127     StringBuffer    strBuf   = new StringBuffer  ();
128     CharacterData charData;
129 
130     while (tempNode != null) {
131       switch (tempNode.getNodeType()) {
132         case Node.TEXT_NODE :
133         case Node.CDATA_SECTION_NODE : charData = (CharacterData)tempNode;
134                                        strBuf.append(charData.getData());
135                                        break;
136       }
137       tempNode = tempNode.getNextSibling();
138     }
139     return strBuf.toString();
140   }
141 
142   /**
143    * Return the first child element of the given element. Null if no
144    * children are found.
145    *
146    * @param elem Element whose child is to be returned
147    * @return the first child element.
148    */
149   public static Element getFirstChildElement (Element elem) {
150     for (Node n = elem.getFirstChild (); n != null; n = n.getNextSibling ()) {
151       if (n.getNodeType () == Node.ELEMENT_NODE) {
152         return (Element) n;
153       }
154     }
155     return null;
156   }
157 
158   /**
159    * Return the next sibling element of the given element. Null if no
160    * more sibling elements are found.
161    *
162    * @param elem Element whose sibling element is to be returned
163    * @return the next sibling element.
164    */
165   public static Element getNextSiblingElement (Element elem) {
166     for (Node n = elem.getNextSibling (); n != null; n = n.getNextSibling ()) {
167       if (n.getNodeType () == Node.ELEMENT_NODE) {
168         return (Element) n;
169       }
170     }
171     return null;
172   }
173 
174   /**
175    * Return the first child element of the given element which has the
176    * given attribute with the given value.
177    *
178    * @param elem      the element whose children are to be searched
179    * @param attrName  the attrib that must be present
180    * @param attrValue the desired value of the attribute
181    *
182    * @return the first matching child element.
183    */
184   public static Element findChildElementWithAttribute (Element elem, 
185                    String   attrName,
186                    String   attrValue) {
187     for (Node n = elem.getFirstChild (); n != null; n = n.getNextSibling ()) {
188       if (n.getNodeType () == Node.ELEMENT_NODE) {
189         if (attrValue.equals (DOMUtils.getAttribute ((Element) n, attrName))) {
190           return (Element) n;
191         }
192       }
193     }
194     return  null;
195   }
196 
197   /** 
198    * Count number of children of a certain type of the given element.
199    *
200    * @param elem the element whose kids are to be counted
201    *
202    * @return the number of matching kids.
203    */
204   public static int countKids (Element elem, short nodeType) {
205     int nkids = 0;
206     for (Node n = elem.getFirstChild (); n != null; n = n.getNextSibling ()) {
207       if (n.getNodeType () == nodeType) {
208         nkids++;
209       }
210     }
211     return nkids;
212   }
213 
214   /**
215    * Given a prefix and a node, return the namespace URI that the prefix
216    * has been associated with. This method is useful in resolving the
217    * namespace URI of attribute values which are being interpreted as
218    * QNames. If prefix is null, this method will return the default
219    * namespace.
220    *
221    * @param context the starting node (looks up recursively from here)
222    * @param prefix the prefix to find an xmlns:prefix=uri for
223    *
224    * @return the namespace URI or null if not found
225    */
226   public static String   getNamespaceURIFromPrefix (Node context,
227                                                   String   prefix) {
228     short nodeType = context.getNodeType ();
229     Node tempNode = null;
230 
231     switch (nodeType)
232     {
233       case Node.ATTRIBUTE_NODE :
234       {
235         tempNode = ((Attr) context).getOwnerElement ();
236         break;
237       }
238       case Node.ELEMENT_NODE :
239       {
240         tempNode = context;
241         break;
242       }
243       default :
244       {
245         tempNode = context.getParentNode ();
246         break;
247       }
248     }
249 
250     while (tempNode != null && tempNode.getNodeType () == Node.ELEMENT_NODE)
251     {
252       Element tempEl = (Element) tempNode;
253       String   namespaceURI = (prefix == null)
254                             ? getAttribute (tempEl, "xmlns")
255                             : getAttributeNS (tempEl, NS_URI_XMLNS, prefix);
256 
257       if (namespaceURI != null)
258       {
259         return namespaceURI;
260       }
261       else
262       {
263         tempNode = tempEl.getParentNode ();
264       }
265     }
266 
267     return null;
268   }
269 
270   public static Element getElementByID(Element el, String   id)
271   {
272       if (el == null)
273           return null;
274       String   thisId = el.getAttribute("id");
275       if (id.equals(thisId))
276           return el;
277       
278       NodeList list = el.getChildNodes();
279       for (int i = 0; i < list.getLength(); i++) {
280           Node node = list.item(i);
281           if (node instanceof Element) {
282               Element ret = getElementByID((Element)node, id);
283               if (ret != null)
284                   return ret;
285           }
286       }
287       
288       return null;
289   }
290 
291   public static QName getQualifiedAttributeValue(Element el,
292                                                  String   attrName)
293     throws IllegalArgumentException  
294   {
295     String   attrValue = DOMUtils.getAttribute(el, attrName);
296 
297     if (attrValue != null)
298     {
299       int    index                 = attrValue.indexOf(':');
300       String   attrValuePrefix       = (index != -1)
301                                      ? attrValue.substring(0, index)
302                                      : null;
303       String   attrValueLocalPart    = attrValue.substring(index + 1);
304       String   attrValueNamespaceURI =
305         DOMUtils.getNamespaceURIFromPrefix(el, attrValuePrefix);
306 
307       if (attrValueNamespaceURI != null)
308       {
309         return new QName(attrValueNamespaceURI, attrValueLocalPart);
310       }
311       else
312       {
313         throw new IllegalArgumentException  ("Unable to determine " +
314                                            "namespace of '" +
315                                            (attrValuePrefix != null
316                                             ? attrValuePrefix + ":"
317                                             : "") + attrValueLocalPart +
318                                            "'.");
319       }
320     }
321     else
322     {
323       return null;
324     }
325   }
326 }
327
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